What are the main terms about voice over rates that I should know?

These are the main terms to consider when negotiating with a client the terms of your agreement on the recording and payment.

Market: Markets can be broken up into local, regional, and national depending on what station or stations they're broadcasted on and what medium ie. radio, television

Buy-Out: a flat rate which “buys” the right to use your voice, in other words, they own the result of the work. 

Per Hour: charging an hourly rate based on the length of time you spend at the studio.

Per Project: charging a flat rate for a script, regardless of the time spent at the studio.

Per Session: charging a flat rate for the recording session (the time you spend in the studio) regardless of the number of projects recorded.

Per Spot: charging a flat rate for each commercial spot, regardless of the time spent at the studio.

Session: the time spent at a recording studio on one given trip. If you leave the studio and come back on a different day, even if you continue to work on the same project, it is a new “session.”

Union Rates: When you're a member of a voice actors union, they advise and promote a minimum set of rates depending on the project's scope and where it will be displayed.